This invention relates to impact-modified styrene-acrylonitrile (SAN) copolymer resins. More particularly, this invention relates to high-impact blends comprising SAN and a cross-linked, polyester elastomer.
Styrene-acrylonitrile copolymers are strong, rigid transparent thermoplastics. SAN resins exhibit outstanding environmental resistance and find wide application for end-uses where exposure to foods, detergents, fuels and the like will occur. These resins are, however, extremely notch sensitive and their impact resistance is correspondingly very poor. SAN copolymers are incompatable with most rubbery polymers such as polybutadiene and the like, hence the rubber modification of SAN resins to improve impact is generally accomplished by graft polymerizing styrene and acrylonitrile monomers in the presence of a rubbery substrate, forming the widely known ABS graft polymer resins.
Linear aliphatic polyester elastomers have long been known in the art. These polymers are compatable with SAN, and blends of SAN with linear, uncross-linked polyesters as well as graft polymers of SAN on linear polyester rubbers have been disclosed in the prior art, as for example, in U.S. Pat. No. 3,577,478. Although these compositions exhibit many useful properties, the impact modification has been marginal.